1. Field of the Invention
The present invention generally relates to the conversion of chemical energy to electrical energy and, more particularly, to an alkali metal electrochemical cell having a cathode current collector provided with a noble metal coating to increase electrical conductivity. A preferred cathode includes a solid active material and a most preferred cathode active material is a carbonaceous material, such as fluorinated carbon (CFx).
2. Prior Art
Conventional Li/CFx cells exhibit degradation in their running voltage when they are built with titanium cathode current collector screens and stored for extended periods of time or are subjected to elevated temperature. To overcome this energy loss, it is known to coat the cathode current collector screen. Carbon paint is a suitable coating material typically used for this purpose. Carbon coating materials enable such cells to operate at increased running potentials, even after 30 days of exposure to 100° C. heat. For example, U.S. Pat. No. 6,451,483 to Probst et al., which is assigned to the assignee of the present invention and incorporated herein by reference, describes a prior art Li/CFx cell including a titanium cathode current collector screen coated with a thin layer of graphite/carbon paint.
While a coating of carbon paint on the cathode current collector screen eliminates the decreased operating potential of Li/CFx cells in comparison to untreated titanium screens, portions of the screen typically need to be masked before the paint is applied. Spot welding through the carbon paint layer for connecting the current collector to the cathode terminal structure typically results in diminished weld integrity.